Experimental studies addressing the longevity of Bacillus subtilis spores – The first data from a 500-year experiment

Abstract

The ability to form endospores allows certain Gram-positive bacteria (e.g. Bacillus subtilis) to challenge the limits of microbial resistance and survival. Thus, B. subtilis is able to tolerate many environmental extremes by transitioning into a dormant state as spores, allowing survival under otherwise unfavorable conditions. Despite thorough study of spore resistance to external stresses, precisely how long B. subtilis spores can lie dormant while remaining viable, a period that potentially far exceeds the human lifespan; is not known although convincing examples of long term spore survival have been recorded. In this study, we report the first data from a 500-year microbial experiment, which started in 2014 and will finish in 2514. A set of vials containing a defined concentration of desiccated B. subtilis spores is opened and tested for viability every two years for the first 24 years and then every 25 years until experiment completion. Desiccated baseline spore samples were also exposed to environmental stresses, including X-rays, 254 nm UV-C, 10% H2O2, dry heat (120°C) and wet heat (100°C) to investigate how desiccated spores respond to harsh environmental conditions after long periods of storage. Data from the first 2 years of storage show no significant decrease in spore viability. Additionally, spores of B. subtilis were subjected to various short-term storage experiments, revealing that space-like vacuum and high NaCl concentration negatively affected spore viability.

Bio-efficacy of Trichoderma isolates and Bacillus subtilis against root rot of muskmelon Cucumis melo L. caused by Phytophthora drechsleri under controlled and field conditions

“…In field experiment percent disease incidence and percent survival rate of plants, second season trial showed good results compared to the first season. Many researchers confirmed that the antagonistic fungi Trichoderma and Bacillus could survive for many years in soil (Longa et al, 2009;Setlow, 2014;Ulrich et al, 2018). So, our experiment confirmed that the population of antagonists was already present in next growing season in the soil because the incidence was minimum while survival rate was increased during second growing season.…”

Resilient living materials built by printing bacterial spores

“…Given the known longevity of spores 61 , it is expected that they would be able to regerminate after indefinite storage under these conditions. Spores can survive under more extreme environmental stresses.…”

Highlights of the Genetics and Importance of Bacillus subtilis Spore Formation

“…Spores are dormant and resistant cell types that serve as adaptive forms by which the bacteria survive extreme environmental stresses [36]. Some of the adverse conditions that the bacteria commonly encounter include bacteriocidal agents such as lysozyme, heat and ultraviolet radiation [37]. A large number of spores of a particular species in a habitat is a strong indication of previous or continuing growth and metabolism in that niche.…”